1. Field of Invention
The present disclosure relates to an electrical submersible pumping system configured to heat fluid to be pumped by the system.
2. Description of Prior Art
Submersible pumping systems are often used in hydrocarbon producing wells for pumping fluids from within the well bore to the surface. These fluids are generally liquids and include produced liquid hydrocarbon as well as water. One type of system used in this application employs an electrical submersible pump (ESP). Submersible pumping systems, such as electrical submersible pumps (ESP) are often used in hydrocarbon producing wells for pumping fluids from within the well bore to the surface. ESP systems may also be used in subsea applications for transferring fluids, for example, in horizontal conduits or vertical caissons arranged along the sea floor. When ESP pumps are deployed in seabed applications they reside in a cold sea water environment with temperatures in the mid 30° F. to 40° F. range. However, when the ESP pump is energized and it is required to handle production fluids at considerably higher temperatures, sometimes in excess of 300° F.
One unique problem associated with these large temperature excursions is difficulty in starting up the system after a shutdown. Crude oil that is easily pumped at production temperatures is often very viscous when it is cooled to sea water temperature, thereby effectively locking the pump stages of the ESP so the pump is unable to be rotated. One way to restart the system is to heat the crude oil in the pump to sufficiently reduce the oil viscosity into a range where the resistance to flow is reduced such that the pump can be restarted. A similar temperature related issue is associated with hydrates which accumulate in the pump when production fluids are cooled, also locking the pump impellers. Like viscous crude, this can be resolved by heating the hydrates and freeing the pump to rotate. In other situations, depending on the fluid characteristics of the oil being pumped, there may be some advantages associated with reducing the fluid viscosity by heating the pump and motor before fully starting the system to reduce the fluid viscosity.